Prediction of forest fire occurrence in China under climate change scenarios

Climate change has an impact on forest fire patterns.In the context of global warming,it is important to study the possible effects of climate change on forest fires,carbon emission reductions,carbon sink effects,forest fire management,and sustainable development of forest ecosystems.This study is based on MODIS active fire data from 2001-2020 and the influence of climate,topography,vegetation,and social factors were integrated.Temperature and precipitation information from different scenarios of the BCC-CSM2-MR climate model were used as future climate data.Under climate change scenarios of a sustainable low development path and a high conventional development path,the extreme gradient boosting model predicted the spatial distribution of forest fire occurrence in China in the 2030s(2021-2040),2050s(2041-2060),2070s(2061-2080),and2090s(2081-2100).Probability maps were generated and tested using ROC curves.The results show that:(1)the area under the ROC curve of training data(70%)and validation data(30%)were 0.8465 and 0.8171,respectively,indicating that the model can reasonably predict the occurrence of forest fire in the study area;(2)temperature,elevation,and precipitation were strongly correlated with fire occurrence,while land type,slope,distance from settlements and roads,and slope direction were less strongly correlated;and,(3)based on future climate change scenarios,the probability of forest fire occurrence will tend to shift from the south to the center of the country.Compared with the current climate(2001-2020),the occurrence of forest fires in 2021-2040,2041-2060,2061-2080,and 2081-2100 will increase significantly in Henan Province(Luoyang,Nanyang,S anmenxia),Shaanxi Province(Shangluo,Ankang),Sichuan Province(Mianyang,Guangyuan,Ganzi),Tibet Autonomous Region(Shannan,Linzhi,Changdu),Liaoning Province(Liaoyang,Fushun,Dandong).

Change of Tillage Layer Thickness of Farmland in Anhui Province of Eastern China

Tillage layer thickness (TLT) of farmland could be regarded as one of physical indexes in assessing soil productivity and quality. In recent years, tillage layer shallowing was found in China in various regions, mainly due to the adoption of non-tillage or rotary tillage practices, but only little rough and non-quantitative information is available so far on the issue. This research took Anhui, a typical agricultural province in Eastern China as an example and compared the TLTs of 87 typical profiles on provincial scale and 210 on county scale from 1980s to 2010s. The results showed that TLTs of 3.7% and 17.2% of samples in 1980s and 2010s respectively were larger than 20 cm. From 1980s to 2010s the mean TLT increased from 16.3 to 17.4 cm on the provincial scale and from 15.0 to 15.5 cm on the county scale respectively. In the middle and southern regions the mean TLTs increased by 0.4-0.7 cm on the provincial scale and 0.3-3.2 cm on the county scale respectively, but decreased by 2.0 cm in northern region on the county scale. The mean TLT increased by 0.8 cm for paddy-field and 1.4 cm for dry-land on the provincial scale. TLT was influenced comprehensively by the factors of soil texture, the depth of rotary tillage and the farming positivity of the farmers. Generally, TLT of farmland with coarse soil texture was higher than that of farmland with fine soil texture, in 1980s TLT in region of poor-economic condition usually was deeper than in region of good-economic condition, and the adoption of rotary tillage led widely TLTs of farmlands to about 15 cm in 2010s.

Onset of Xiashu loess deposition in southern China by 0.9 Ma and its implications for regional aridification

The Xiashu loess is a typical Quaternary eolian deposit in southern China and represents an important terrestrial paleoclimate archive in this low-latitude monsoon region. However, the chronological framework of Xiashu loess deposition has yet to be established. Determining the timing of the onset of Xiashu loess deposition will allow researchers to better understand late Quaternary aridification across the Asian continent, the evolution of the East Asian monsoon and regional environmental changes in subtropical regions. Therefore, in this study, a systematic chronological study of the Xiashu loess is conducted to answer this question. For the first time, magnetostratigraphic classification reveals that the Matuyama/Brunhes(M/B) reversal is present in the Xiashu loess at two sites in Jiangsu Province, the Qingshan profile at Yizheng and the Dagang core in Zhenjiang.Based on the results of magnetostratigraphy and optically stimulated luminescence(OSL) dating, the age of the lower boundary of the Xiashu loess is estimated to be approximately 0.9 Ma. Consequently, this Xiashu loess deposit is the oldest reported to date and is comparable in age to the red soil deposit in Xuancheng, Anhui Province. The onset of Xiashu loess deposition by 0.9 Ma represents the further expansion of arid range in Asia in the late Quaternary in response to significant aridification and winter monsoon strengthening in this subtropical region. We suggest that these climate changes were primarily driven by global cooling and an increase in high-latitude ice volume in the Northern Hemisphere and that the initiation of Xiashu loess accumulation was a regional response of southern China to the 0.9 Ma global cooling event.